1. Field of the Invention
The present invention relates to a multi-layer electromagnetic wave absorber and a manufacturing method thereof. More particularly, the present invention relates to a multi-layer electromagnetic wave absorber with a thin thickness for improving an absorption performance in broadband communications and a manufacturing method thereof.
2. Description of the Related Art
Recently, as digital technology and the semiconductor industry have been rapidly developed, miniaturized and lightweight electrical devices for high speed and broadband services are being developed. However, electrical devices are sensitive to minute electromagnetic wave disturbances such that they can easily cause a malfunction in operation of the electrical devices.
As a countermeasure against such electromagnetic wave disturbances, an electromagnetic wave shielding technique for reflecting and shielding the electromagnetic wave with metal may be implemented. Also, an electromagnetic wave absorbing technique for absorbing the electromagnetic wave by an electromagnetic wave absorber may be implemented. However, recently, the electromagnetic wave absorbing technique has been widely used, because the electromagnetic wave shielding technique induces additional damage due to the shielded electromagnetic wave.
FIG. 1 is a cross-sectional view of a single layer electromagnetic wave absorber according to the related art.
Referring to FIG. 1, the single layer electromagnetic wave absorber 100 includes an absorption layer 120 and a boundary layer 130 laminated on the rear side of the absorption layer 120. The absorption layer 120 includes a dielectric lossy material or a magnetic lossy material, so as to absorb an electromagnetic wave. The boundary layer 130 is made of a highly conductive electric conductor in order to block and reflect an electromagnetic wave which is not absorbed by the absorption layer 120.
FIG. 2 is a graph illustrating a reflection loss according to a frequency of the single layer electromagnetic wave absorber shown in FIG. 1.
In FIG. 2, thicknesses of the absorption layer 120 are differentiated by a two-dot chain line, an alternate long and short dash line, and a solid line, which respectively indicate thicknesses of 2.0 mm, 3.0 mm and 4.0 mm. As shown in FIG. 2, the single layer electromagnetic wave absorber 100 has an absorption performance in one vertex A of 10 GHz, which is the center frequency of the X-band frequency range of 8.2˜12.4 GHz. Hence, a 10 dB absorption band width (a bandwidth absorbing 90% or more of an incident electromagnetic wave) is about 2.6˜6.4 GHz, which means that the absorption bandwidth is too narrow. Accordingly, a multi-layer electromagnetic wave absorber is used so as to broaden the absorption bandwidth. This conventional multi-layer electromagnetic wave absorber is composed of a surface layer, an absorption layer and a boundary layer. The surface layer and the absorption layer include only one of a dielectric lossy material and magnetic lossy material. Accordingly, although the absorption bandwidth of the conventional multi-layer electromagnetic wave absorber becomes wider than the single layer electromagnetic wave absorber, a thickness of the multi-layer electromagnetic wave absorber becomes too large.